Acrylic yarn package

ABSTRACT

An acrylic yarn package prevents winding yarn collapse during transportation when an acrylic yarn having a high total fineness is wound around a core bobbin. The acrylic yarn package includes an acrylic yarn wound around a bobbin and having a total fineness of 8000 dtex or more. The acrylic yarn on the package has a yarn width of 0.22 mm/1000 dtex or more and hardness of 60 or more.

TECHNICAL FIELD

This disclosure relates to an acrylic yarn package, and an acrylic yarnpackage having a good package shape and less troubles duringtransportation and unwinding. In particular, the package is suitable asan acrylic precursor yarn package used for production of carbon fibers.

BACKGROUND

Polyacrylonitrile long fibers have been used not only as clothing butalso precursors of carbon fibers in recent years, and many improvementtechniques have been disclosed to obtain carbon fibers having excellentperformance and increase their productivity.

The carbon fibers are obtained by winding an acrylonitrile fiber yarn asa precursor once in a yarn-making process of spinning the acrylonitrilefiber yarn, and then sending the acrylonitrile fiber yarn to acarbonization process in which the fiber is heated in an air atmosphereat 200 to 300° C. to convert the fiber into an oxidized fiber (oxidationprocess), and the oxidized fiber is further heated to 300 to 3000° C. inan inert atmosphere such as nitrogen, argon, or helium to convert theoxidized fiber into a carbon fiber (carbonizing process). The carbonfibers are widely utilized as reinforcing fibers for composite materialsin aerospace applications, sports applications, and general industrialapplications and the like.

The carbon fiber generally includes a multifilament composed offilaments having 1000 or more monofilaments as one yarn unit, butbecause of a difference in production yarn speed between a yarn-makingprocess and a carbonization process as a subsequent process, an acrylicyarn as a raw material is generally wound once in the yarn-makingprocess, and then sent to the carbonization process. To increaseproductivity in the carbonization process, it is effective to increasethe amount of an acrylic yarn that can be processed per one time.However, the acrylic yarn is usually wound around a core bobbin so that,if a large amount of yarn is wound around one bobbin, the bobbin may sagin a vertical direction during transportation of the bobbin to thecarbonization process, or bulge in side surfaces may increase, to resultin winding yarn collapse causing unwinding failure in the carbonizationprocess.

Japanese Patent Laid-open Publication No. 11-263534 describes atechnique for defining winding conditions such as a taper angle andwinding tension in an acrylic yarn package for precursors of carbonfibers to obtain a good package shape during winding. However, JP '534describes no winding yarn collapse during transportation. JapanesePatent Laid-open Publication No. 2002-3081 describes a technique forobtaining a good package shape by taking a specific yarn width and yarnshift ratio for a thick acrylic yarn of 33000 dtex or more. However,unless moisture is applied to the yarn before winding to improve thebundling property, deterioration in the package shape and trouble duringunwinding cannot be completely prevented. This causes a problem thatwinding yarn collapse occurs even during transportation. Because of theapplication of moisture, the technique has the problem that the runningcost increases and it is not suitable for long-distance movement due toan increase in mass.

Furthermore, Japanese Patent Laid-open Publication Nos. Sho51-23322 and2005-273106 describe techniques for defining the hardness of a packagefor fibers having a total fineness of several tens to several hundredsdtex to prevent winding yarn collapse during transportation. However,those techniques cannot be directly applied to an acrylic yarn packagefor precursors of carbon fibers having a high total fineness exceeding1000 dtex.

It could therefore be helpful to provide an acrylic yarn package thatprevents winding yarn collapse during transportation when an acrylicyarn having a high total fineness is wound around a core bobbin.

SUMMARY

We thus provide an acrylic yarn package including an acrylic yarn woundaround a bobbin and having a total fineness of 8000 dtex or more,wherein the acrylic yarn on the package has a yarn width of 0.22 mm/1000dtex or more and hardness of 60 or more.

Our acrylic yarn package has a good package shape and prevents collapseduring transportation of an acrylic yarn package having a high totalfineness to a next process when the acrylic yarn is wound around a corebobbin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an acrylic yarn package.

FIG. 2 is a schematic view showing an acrylic yarn package havingwarpage occurring in its center.

DESCRIPTION OF REFERENCE SIGNS

-   1: Acrylic yarn package-   2: Core bobbin-   3: Acrylic yarn-   4: Acrylic yarn-   5: Straight line connecting both ends of upper part of package-   6: Curve following upper part of package-   L: Yarn traverse width-   k1, k2: Bulge length in side surfaces-   S: Yarn shift length-   T: Yarn width-   U: Warpage-   θ: Taper angle-   α: Line perpendicular to core bobbin axis direction

DETAILED DESCRIPTION

We considered the problems associated with a carbon fiber precursoracrylic thick yarn package having a good package shape withoutcollapsing even during transportation when an acrylic yarn having a hightotal fineness is wound around a core bobbin as the above problems, anddiscovered that improvements are possible by setting the yarn width andhardness of the package to a certain level or higher.

The carbon fiber precursor acrylic yarn is composed of a so-calledacrylic polymer, for example, preferably a polymer obtained bypolymerizing 90% by mass or more of acrylicnitrile and less than 10% bymass of a comonomer. Examples of the comonomer include at least oneselected from acrylic acid, methacrylic acid, itaconic acid, and methylester, ethyl ester, propyl ester, and butyl ester of these acids; alkalimetal salt, ammonium salt, or allyl sulfonic acid, methallyl sulfonicacid, alkali metal salts thereof and the like.

Such an acrylic polymer can be obtained by using a known polymerizationmethod, for example, a polymerization method such as emulsionpolymerization, suspension polymerization, or solution polymerization.When an acrylic fiber is produced from these polymers, a polymersolution containing a solvent selected from, for example, dimethylacetamide, dimethyl sulfoxide (DMSO), dimethylformamide, aqueoussolutions of nitric acid, zinc chloride, and sodium rhodanide is used asa spinning raw yarn, and spinning is performed by a wet spinning methodor a dry spinning method.

The spun yarn is then subjected to bath draw, but the spun-out yarn maybe directly subjected to the bath draw, or the spun-out yarn may bewashed with water once to remove the solvent, followed by subjecting thespun yarn to the bath draw. In such a bath draw, the spun yarn ispreferably drawn about 2 to 6 times in a drawing bath at 50 to 98° C.After drawing, an oil agent is preferably applied to the spun yarn, andthe spun yarn is subjected to drying and densification with a hot rolleror the like. Then, the spun yarn is subjected to steam drawing, and thenwound around a core bobbin to form a package.

When such a package is formed, a plurality of yarns may be combined, andthen wound. It is effective to carbonize multifilament yarns at one timeto improve productivity of carbon fibers. Therefore, the total finenessof the wound yarn is 8000 dtex or more. The moisture percentage of theyarn is preferably 3% or less to avoid an increase in mass duringtransportation. The total amount of the acrylic yarn obtained bysubtracting bobbin mass and the amount of moisture from the mass of theentire package is preferably large, preferably 120 kg or more, and morepreferably 200 kg or more to reduce the set number of the acrylic yarnin a carbonization process to improve efficiency.

It is important that the hardness of a bobbin end measured by adurometer is 60 or more to eliminate winding yarn collapse duringtransportation. If the hardness is less than 60, the package is apt toloosen, which can cause winding yarn collapse during transportation andyarn drop during unwinding to occur. The hardness of 60 or more can beachieved by setting the tension of the yarn during winding to anappropriate value. A large amount of yarn is commonly wound while alarge tension is gradually attenuated, but the value may be anappropriate value depending on the fineness of the yarn and the numberof filaments.

It is necessary to wind the acrylic yarn on the package with the yarnwidth of the acrylic yarn set to 0.22 mm/1000 dtex or more. If the yarnwidth is smaller than 0.22 mm/1000 dtex, the thickness of the yarnbecomes large so that a gap causing yarn slip occurs between a yarn andanother yarn adjacent to the yarn, which can cause winding yarn collapseduring transportation. If the yarn width is more than 0.54 mm/1000 dtex,the yarn convergency deteriorates, which may cause trouble such as yarndrop and monofilament wrapping to occur during unwinding in thecarbonization process, whereby the yarn width of the acrylic yarn on thepackage is preferably 0.22 mm to 0.54 mm/1000 dtex. The method ofsetting the yarn width on the package within the above range is notparticularly limited, but when the yarn is wound with a winder, a methodof winding the yarn after causing a group of free rollers for bundlingto pass at a certain level or more is suitably used.

When the coefficient of static friction between the acrylic yarns isless than 0.13, a bulge in side surfaces may occur during winding evenif the yarn width and the hardness are controlled to specific conditionsto prevent the winding yarn collapse. Therefore, the coefficient ofstatic friction is preferably 0.13 or more by applying an appropriatetype and amount of an oil agent.

It is preferable to set a yarn shift ratio to 15 to 59% and a taperangle on the package to 6 to 14°. The yarn shift ratio is a ratio of ayarn shift length S to a yarn width T in two yarns passing through theclosest points on the package in parallel. That is, this yarn shiftratio is obtained by (S/T)×100 shown in FIG. 1. This will beconceptually described using FIG. 1. An acrylic yarn 4 is a yarn passingthrough the closest point on an acrylic yarn package 1 in parallel to anacrylic yarn 3. The yarn shift ratio is a ratio of the yarn shift lengthS between the acrylic yarn 3 and the acrylic yarn 4 to the yarn width T.The yarn width T and the yarn shift length S are values measured bymethods to be described later.

As shown in FIG. 1, the taper angle is an angle (A) between a straightline perpendicular to the axis of a core bobbin 2 (line α perpendicularto the axis direction of the core bobbin) and the direction of theacrylic yarn 4 to be wound.

The yarn shift ratio and the taper angle can usually be controlled bysetting the number of revolutions of a winder spindle per threadtraverse, i.e., a so-called winding ratio to appropriate values. If thewinding ratio is an integer, the yarn passes through the exactly sameyarn passage before and after one traverse, whereby the yarn passagebefore and after one traverse can be shifted by setting the fractionalportion of the winding ratio to an appropriate value, to control theyarn shift ratio. The taper angle can be controlled by setting the sizeof the entire winding ratio including an integer portion to anappropriate value.

If the yarn shift ratio is less than 15%, the package has largeundulations. Even if a winding tension is increased, the hardness may bedecreased, which can cause the winding yarn collapse to occur duringtransportation. When the yarn shift ratio is more than 59%, a contactsurface between an inner layer yarn and an outer layer yarn is small sothat the pressing of the outer layer yarn during winding causes theinner layer yarn to slip, to push out the inner layer yarn, which causesa bulge in side surfaces. Therefore, the yarn shift ratio is 15% to 59%,whereby both the hardness and the end face shape can have good values.

If the taper angle is less than 6°, the yarn drop during unwinding islikely to occur. If the taper angle is more than 14°, the bulge in sidesurfaces is large so that the taper angle is preferably 6 to 14°. Whenthe yarn is wound with a constant winding ratio, the taper anglelinearly decreases as the diameter of the package wound around the corebobbin increases, whereby the yarn can be wound while the taper angle iskept within a certain range by changing the winding ratio during windingdepending on the winding amount of the yarn. For example, by providing amechanism such that spindle drive and traverse drive are made to beindependent from each other, the number of revolutions of the spindle isdetected, calculation is performed to provide the set winding ratio, andthen the number of revolutions of the traverse drive is controlled, thewinding ratio can be freely set depending on the wilding amount in thewinding process.

EXAMPLES

Hereinafter, our yarn packages will be described in detail withreference to Examples and Comparative Examples. Measurement methods usedin Examples and Comparative Examples will be described below.

Total Fineness

A sample yarn of 20 m was collected from a package to be measured, and atotal fineness was determined by a method according to JIS L1013: 2010.

Coefficient of Static Friction

A sample yarn of 1.5 m was collected from a package to be measured, andwrapped around the collected package. At this time, the sample yarn waswound around the center of the package along the circumferential surfaceof the package. After the sample yarn was wound so that a contact anglewith the package was 540°, a weight of 150 g was attached to each ofboth ends of the sample yarn. Then, the mass of the weight on one endside of the yarn was increased, and a mass of the weight when the yarnstarted to slip on a package was measured. A coefficient of staticfriction was calculated from the following formula:

Coefficient of static friction (μs)=3/π×Ln(T1/150)

π: Circumference ratio

T1: Mass of weight (g) when yarn starts to slip.

Yarn Width

Using a caliper, the yarn width of the acrylic yarn on the package wasmeasured at a total of five points of places within 2 cm from both endsof the package (both ends), a center of the package, a place between oneof both the ends and the center, and a place between the other end andthe center, and a value obtained by dividing the measured value with thetotal fineness was taken as the yarn width.

Yarn Shift Ratio

For two yarns passing through the closest points on the package inparallel, a yarn shift length (S) shown in FIG. 1 was measured at atotal of five points of both ends of the package, a center of thepackage, a place between one of both the ends and the center, and aplace between the other end and the center using a caliper, and a valueobtained by dividing the average value with the yarn width was taken asthe yarn shift ratio.

Taper Angle Range

While the wound package was subjected to unwinding, an angle (θ) betweena straight line (α) perpendicular to the axial direction of a corebobbin 2 shown in FIG. 1 and the direction of a yarn 4 to be wound wasmeasured at the center of the package every 10 kg until all the yarnswere discharged, and the range of the measured value was taken as ataper angle range. Hardness

Using HARDNESS TESTER “Type C” (for Cellular Rubber & Yarn Package)manufactured by KOBUNSHI KEIKI CO., LTD., values were measured at twoplaces within 2 cm from both ends of the package, and the average valuethereof was taken as the hardness of the yarn package.

Winding Yarn Collapse during Transportation

An acrylic yarn package was set at a trolley with a spindle, and oneacrylic yarn package subjected to a transportation vibration testaccording to JIS Z 0232: 2004 once to determine the presence or absenceof winding yarn collapse according to the following two levels: Good: Noincrease of 5.0 mm or more of bulge in side surfaces and no increase of10 mm or more of warpage.

Poor: Increase of 5.0 mm or more of bulge in side surfaces and increaseof 10 mm or more of warpage.

A distance (U) between a straight line 5 connecting both ends of anupper part of the package shown in FIG. 2 and the farthest point on acurve 6 following the upper part of the package was measured, and takenas warpage U.

Bulge in Side Surfaces

Bulge length in side surfaces (k1, k2), which was a height of a pointwhere a side surface of the package bulges on the outermost side, withrespect to a yarn traverse width (L) on the outermost surface of thepackage, as shown in FIG. 1 was measured on each of both the sidesurfaces of the package, and the average value thereof was taken asbulge in side surfaces.

Trouble During Unwinding

When the package was set on a creel, and the entire amount was subjectedto unwinding, those that did not cause yarn drop or monofilamentwrapping were taken as good, and those that caused yarn drop ormonofilament wrapping were taken as poor.

Example 1

Using a 19% DMSO solution of an acrylic polymer having an intrinsicviscosity [η] of 1.80 and containing 99.6% by mass of acrylonitrile and0.4% by mass of itaconic acid as a raw spinning solution, and aspinneret having 6000 pores, semi-wet spinning was performed in acoagulation bath containing 30% of DMSO and 70% of water at 8° C. toobtain a coagulated yarn. The coagulated yarn was drawn 2.8 times in hotwater while being washed with water. Furthermore, the remaining DMSO waswashed with water until the DMSO amount became 0.01% or less in theyarn, and a silicone-based oil agent was then applied, followed bydrying and densification at 150 to 160° C. Subsequently, the yarn wasdrawn 4.3 times in pressurized steam, and then dried again. Two6000-filament yarns were combined, and a 12000-filament yarn having atotal fineness of 13300 dtex was wound around an FRP core bobbin havingan outer diameter of 145 mm with a winder so that the total amount ofthe acrylic yarn obtained by subtracting the bobbin mass and the amountof moisture from the mass of the entire package was 120 kg in a yarnwidth, a yarn shift ratio, and a taper angle range shown in Table 1. Theamount of moisture was determined by collecting a yarn of about 12 m tobe wound in advance, measuring a moisture percentage by a methodaccording to JIS L1013: 2010, and multiplying the moisture percentage bythe amount of the wound yarn.

As a result, as shown in Table 1, a good package which did not causewinding yarn collapse during transportation was provided.

Examples 2 to 5 and Comparative Examples 1 to 4

An acrylic yarn was wound in a yarn width, a yarn shift ratio, and ataper angle range shown in Table 1 in the same manner as in Example 1except that the total weight of the acrylic yarn obtained by subtractinga bobbin mass and an amount of moisture from the mass of an entirepackage was set to 240 kg, and a yarn width during winding, and awinding ratio and tension of a winder were changed.

As a result, as shown in Table 1, Examples 2 to 5 provided a goodpackage that did not cause winding yarn collapse during transportation,but Example 4 caused a high yarn shift ratio of 60% or more duringwinding, to result in a small contact surface between an inner layeryarn and an outer layer yarn so that the outer layer yarn pressed theinner layer yarn during winding, and the inner layer yarn slid and waspushed out, to result in a package having a large bulge in sidesurfaces. Example 5 caused a large yarn width of 0.55 mm/1000 dtex ormore to result in poor yarn convergency so that yarn drop andmonofilament wrapping occurred during unwinding in a carbonizationprocess. Comparative Examples 1 to 3 had hardness of less than 60 ascompared to Example 2, and caused winding yarn collapse duringtransportation. Comparative Example 4 had a yarn width of less than 0.22mm/1000 dtex as compared to Example 2, and caused winding yarn collapseduring transportation.

Examples 6 and 7

A yarn was wound in a yarn width and a yarn shift ratio shown in Table 1in the same manner as in Example 2 except that the amount of an oilagent deposited was adjusted to change the coefficient of staticfriction of the yarn. As a result, as shown in Table 1, a good packagethat did not cause winding yarn collapse during transportation wasprovided. Example 6 had a low coefficient of static friction of lessthan 0.13 and caused yarn lateral sliding during winding, to result in apackage having large bulge in side surfaces.

Example 8

A 24000-filament yarn having a total fineness of 26600 dtex was wound ina yarn width and a yarn shift ratio shown in Table 1 in the same manneras in Example 2 except that four 6000-filament yarns were combined.

As a result, as shown in Table 1, a good package that did not causewinding yarn collapse during transportation was provided.

Example 9

A 24000-filament yarn having a total fineness of 29100 dtex was wound ina yarn width and a yarn shift ratio shown in Table 1 in the same manneras in Example 8 except that a drawing ratio in pressurized steam was3.9.

As a result, as shown in Table 1, a good package that did not causewinding yarn collapse during transportation was provided.

Example 10

A 36000-filament yarn having a total fineness of 26600 dtex was wound ina yarn width and a yarn shift ratio shown in Table 1 in the same manneras in Example 2 except that six 6000-filament yarns having amonofilament fineness of 0.74 dtex were combined.

As a result, as shown in Table 1, a good package that did not causewinding yarn collapse during transportation was provided.

TABLE 1-1 Coefficient Yarn Yarn Taper Total Winding of static widthshift angle fineness amount friction [min/ ratio range Hardness [dtex][kg] [−] 1000 dtex] [%] [°] [−] Example 1 13300 120 0.15 0.40 54 7 to 1375 Example 2 13300 240 0.15 0.40 54 7 to 13 75 Example 3 13300 240 0.140.37 19 7 to 13 64 Example 4 13300 240 0.15 0.40 60 7 to 13 74 Example 513300 240 0.16 0.67 50 7 to 13 70 Example 6 13300 240 0.10 0.38 50 7 to13 74 Example 7 13300 240 0.22 0.40 54 7 to 13 78 Example 8 26600 2400.15 0.26 57 7 to 13 77 Example 9 29100 240 0.17 0.30 40 7 to 13 81Example 10 26600 240 0.16 0.29 28 7 to 13 79 Comparative 13300 240 0.150.37 10 7 to 13 59 Example 1 Comparative 13300 240 0.15 0.40 54 3 to 1655 Example 2 Comparative 13300 240 0.15 0.40 54 7 to 13 55 Example 3Comparative 13300 240 0.16 0.21 50 7 to 13 65 Example 4

TABLE 1-2 Bulge in side surfaces Numerical Trouble Winding yarn collapseduring value during transportation [mm] Determination unwinding Example1 Good 14 Very good Good Example 2 Good 20 Good Good Example 3 Good 18Good Good Example 4 Good 26 Poor Good Example 5 Good 24 Good PoorExample 6 Good 28 Poor Good Example 7 Good 21 Good Good Example 8 Good24 Good Good Example 9 Good 22 Good Good Example 10 Good 22 Good GoodComparative Poor 22 Good Good Example 1 Comparative Poor 29 Poor PoorExample 2 Comparative Poor 22 Good Good Example 3 Comparative Poor 23Good Good Example 4 No winding yarn collapse: good Less than 15 mm: verygood No trouble: good Winding yarn collapse: poor Less than 25 mm: goodTrouble: poor 25 mm or more: poor

1-4. (canceled)
 5. An acrylic yarn package comprising an acrylic yarnwound around a bobbin and having a total fineness of 8000 dtex or more,wherein the acrylic yarn on the package has a yarn width of 0.22 mm/1000dtex or more and hardness of 60 or more.
 6. The acrylic yarn packageaccording to claim 5, wherein a total amount of the acrylic yarn is 120kg or more.
 7. The acrylic yarn package according to claim 5, whereinthe acrylic yarn has a coefficient of static friction of 0.13 or more.8. The acrylic yarn package according to claim 5, wherein the acrylicyarn on the package has a yarn width of 0.22 to 0.54 mm/1000 dtex, ayarn shift ratio of 15 to 59%, and a taper angle of 6 to 14°.
 9. Theacrylic yarn package according to claim 6, wherein the acrylic yarn hasa coefficient of static friction of 0.13 or more.
 10. The acrylic yarnpackage according to claim 6, wherein the acrylic yarn on the packagehas a yarn width of 0.22 to 0.54 mm/1000 dtex, a yarn shift ratio of 15to 59%, and a taper angle of 6 to 14°.
 11. The acrylic yarn packageaccording to claim 7, wherein the acrylic yarn on the package has a yarnwidth of 0.22 to 0.54 mm/1000 dtex, a yarn shift ratio of 15 to 59%, anda taper angle of 6 to 14°.
 12. The acrylic yarn package according toclaim 9, wherein the acrylic yarn on the package has a yarn width of0.22 to 0.54 mm/1000 dtex, a yarn shift ratio of 15 to 59%, and a taperangle of 6 to 14°.